The present invention relates generally to radar systems and Electronic Warfare (EW) systems, and in particular, to high power transmitters used in these systems.
This application is related by subject-matter to the application entitled xe2x80x9cEfficient Beam Steering For Closed Loop Polarization Agile Transmitterxe2x80x9d , Ser. No. 10/052,522, filed in the name of inventors Martin J. Apa, Joseph Cikalo, William L. High, and Mitchell J. Sparrow.
to Electronic Warfare (EW) generally relates to any military action involving the use of electromagnetic and directed energy to control the electromagnetic spectrum or to attack the enemy. The three major subdivisions within EW are Electronic Attack, Electronic Protection and Electronic Support. Electronic Attack (EA) is the division of EW involving the use of electromagnetic or directed energy to attack personnel, facilities or equipment with the intent of degrading, neutralizing or destroying enemy combat capability. Transmitters used for an EW system should be small in size, low in weight, and able to carry many watts/cubic inch. In addition, there is often a need in EW systems for a higher power transmitter that is also polarization agile.
One objective of an EW system may be to produce a jamming signal (e.g. false targets) in threat radar receiver that is much greater in amplitude than that of the radar signal reflected by the target aircraft, with the appropriate polarization. The availability of advanced power amplification technologies makes it possible to develop high power transmitters with the above characteristics.
The basic architecture of such a transmitter is an active aperture antenna consisting of a large number of elements. Though the output power of each antenna element is a relatively low level, a high power Radio Frequency (RF) signal is obtained by combining the individual signals in space. To attain the highest power levels, a phase focusing technique is employed. Each element is tuned to produce a signal with the appropriate phase in order to spatially combine. However, phase focusing also produces a narrow beam antenna. Consequently, a beam steering network is used in order to radiate the maximum transmitted signal in a desired direction. Generally, a beam steering network may comprise a network of variable phase shifters, time delay elements, or fiber optic delays, with an external processor and drivers to adjust them.
According to the conventional approach, the phase shifters are inserted at the output terminal of the system""s power amplifiers, just prior to feeding the RF radiators (antenna module). A significant drawback of this architecture is that a large amount of RF power is dissipated in the phase shifters placed after the power amplifiers. This reduces the efficiency of the system and may require the use of additional cooling system capability. Moreover, dissipation of a large amount of RF power in such architecture generally requires use of large, less reliable high power phase shifters that must be capable of handling high RF power levels. The requirement for large size phase shifters makes such transmitter systems used in EW equipment more bulky, less accurate, and less agile. These are significant drawbacks of the prior art.
Other problems and drawbacks also exist.
An embodiment of the present invention comprises a polarization control module and a polarization agile transmitter. The polarization agile transmitter includes a plurality of beam steering phase shifters, a plurality of power amplifier modules and a plurality of dual polarization radiators, where the beam steering phase shifters are located before the power amplifier modules.
According to another aspect of the invention the polarization control module has a receive polarimeter for determining the polarization parameters of the incoming RF signal and a transmit polarimeter for controlling the polarization parameters of transmitted RF signal.
According to yet another aspect of the invention, a receiver is provided to provide a signal base for the polarization agile transmitter.
According to another aspect of the invention, the output signal from the polarization control module is input to the plurality of beam steering phase shifters that comprises a beam steering network placed before the power amplification modules.
Accordingly, it is one object of the present invention to overcome one or more of the aforementioned and other limitations of existing systems for antenna beam steering.
It is another object of the present invention to provide an efficient system for antenna beam steering using low power phase shifters.
It is yet another object of the present invention to provide a system for antenna beam steering that solves or mitigates the problems associated with the requirement of high power beam steering phase shifters.
It is another object of the present invention to provide a system for antenna beam steering that is smaller, lighter and more reliable.
The accompanying drawings are included to provide a further understanding of the invention and are incorporated in and constitute part of this specification, illustrate several embodiments of the invention and, together with the description, serve to explain the principles of the invention. It will become apparent from the drawings and detailed description that other objects, advantages and benefits of the invention also exist.